Amphotericin B susceptibility testing of yeasts with a bactec radiometric system

The effect of amphotericin B on CO(2) production was studied using a Bactec 225. A radiometric procedure for yeast susceptibility testing that requires 3 h of incubation was developed. A total of 48 yeast isolates was tested in this system and the results were correlated to tube dilution studies. The drug concentration causing at least a 44% decrease in CO(2) production correlated to the tube dilution minimal inhibitory concentration in 85% of isolates tested and was within one tube dilution of the minimal inhibitory concentration in over 95% of yeasts tested.